1. Technical Field
The present invention relates to an image formation device such as a photocopier, a printer or the like which employs an electrophotographic system, and more particularly relates to an image formation device which includes a contact charging-type charging roller and a cleaning member of the charging roller, the charging roller rotating and contacting an image-bearing body which is driven to rotate and electrostatically charging a surface of the image-bearing body.
2. Related Art
In recent years, as charging apparatuses for image formation devices such as photocopiers, printers and the like which employ electrophotographic systems, in order to facilitate reductions in ozone emissions, reductions in device sizes, reductions of costs of high-power supplies and so forth, bias charge rollers (BCR) which contact or are disposed close to image-bearing bodies have been employed instead of conventional non-contact-type chargers such as scorotrons and the like.
In a charging apparatus with such a non-contact type charging system, because the charging roller constantly contacts the image-bearing body, there is a problem in that soiling tends to occur because of adherence of extraneous matter to the surface of the charging roller. The image-bearing body repeatedly performs an image formation operation. At a downstream side from a transfer stage, the surface of the image-bearing body passes through a cleaning stage, which removes extraneous matter such as residual toner after transfer and the like, and then advances into a region of a charging stage. However, even though the surface has passed through the cleaning stage, particles which are finer than the toner, such as bits of the toner, external additives of the toner and the like, remain on the image-bearing body rather than being cleaned, and adhere to the surface of the charging roller. The extraneous matter that adheres to the surface of the charging roller causes variations in surface resistance values of the charging roller. Thus, unusual charging, unstable charging and the like occur, and charging uniformity deteriorates.